Apparatuses and systems used for spectroscopic analysis are described; for example, analyzers used for detection of fluorescent X-ray spectra.
X-ray fluorescence detection is a commonly used technique in X-ray absorption spectroscopy applications on dilute systems. As would be appreciated by those skilled in the art, the fluorescence signal from the absorption of spectroscopically interesting atoms forms only a small part of a large background spectrum from various sources including coherent and incoherent scattering of X-ray photons.
Statistical fluctuations in the number of scattered background photons are a principal source of noise and significantly degrade the signal-to-noise ratio in X-ray absorption measurements. Thus, discrimination between the desired X-ray fluorescence and the undesired background is essential for fluorescence detection.
For very dilute systems where the background count rate is 10-1000 or more times greater than the signal count rate, energy-resolving detectors with a reasonable solid angle are more desirable. For example, the 13-element pure germanium detector (manufactured by Canberra Corp., with a corporate headquarters in Meriden, Conn., USA) was designed for this purpose. That detector provides an energy resolution of 200 eV at 6 keV and a high total count rate of approximately 2×106 counts/s.
One difficulty with a pure germanium (Ge) detector lies in dead-time losses originating from its associated pulse-counting electronics. Without certain precautions, it is possible that absorption spectra may be distorted. Moreover, the maximum count rate of the detector itself limits the efficiency of data collection.
Modern synchrotron sources that exist currently generate a spectral flux that often exceeds the detector rate limit for Ge detectors. Since stronger sources are being and have been developed, this problem has become worse and will continue to do so.
An increased photon flux, on the order of 1011-1014 photons/s, provides improved opportunities for X-ray spectroscopy applications in probing dilute systems and rapid reactions. However, in dilute systems, such as those involving trace elements in biological and environmental sciences, an increased photon flux is expected to have little positive effect on spectroscopy data collection. Simply put, the efficiency and sensitivity of existing detectors limits the spectroscopic capability of modern synchrotron sources.
Accordingly, a need has developed for detectors and detector systems that operate, without detector saturation, in high photon flux environments to improve detection and data collection efficiency with a reasonable solid angle.
Development of X-ray fluorescence detectors using a multilayer analyzer array provides improved background discrimination.
The application of the detectors is not limited to X-ray absorption spectroscopy. It can be used in X-ray fluorescence analysis and fluorescence imaging.
One report was that linearly graded multilayers provide reasonable background rejection. However, a multilayer analyzer with linearly graded multilayers is limited in that this type of detector has a limited detection solid angle, restricted by the detector's vertical and horizontal acceptance.
Accordingly, a need remains in the industry for a detector that does not present such limitations in detection and analysis.